Dibenzimidazole grease thickening agents

ABSTRACT

DIBENZIMIDAZOLE COMPOUNDS CORRESPONDING TO THE FORMULA: 2-((5-(R1-X-CO-NH-R4-NH-CO-NH-)BENZIMIDAZOL-2-YL)-R3-), WHEREIN R1 AND R2 ARE ALIPHATIC HYDROCARBYL RADICALS, R3 IS A HYDROCARBYLENE RADICAL, R4 AND R5 ARE AROMATIC HYDROCARBYLENE RADICALS AND X IS -O- OR -NH5-(R2-X-CO-NH-R5-NH-CO-NH-)BENZIMIDAZOLE ARE HIGHLY EFFICACIOUS GREASE THICKENING AGENTS.

United States Patent O 3,785,979 DIBENZIMIDAZOLE GREASE THICKENINGAGENTS August H. Birke, Godfrey, Ill., assignor to Shell Oil Company NoDrawing. Continuation-in-part of abandoned application Ser. No. 169,459,Aug. 5, 1971. This application Oct. 11, 1972, Ser. No. 296,733

Int. Cl. ClOrn /20 US. Cl. 252-515 A Claims ABSTRACT OF THE DISCLOSUREDibenzimidazole compounds corresponding to the formula:

wherein R and R are aliphatic hydrocarbyl radicals, R is ahydrocarbylene radical, R and R are aromatic hydrocarbylene radicals andX is -O-- or are highly eificacious grease thickening agents.

CROSS-REFERENCE TO RELATED APPLICATIONS This application is acontinuation-in-part of copending US. application Ser. No. 169,459,filed Aug. 5, 1971, and now abandoned.

BACKGROUND OF THE INVENTION Field of the invention.-'Ihis inventionrelates to a novel class of dibenzimidazole compounds and greasecompositions gelled therewith.

Description of the prior art.-It has becomeincreasingly important thatgrease compositions be able to provide adequate lubrication at hightemperatures, e.g., temperatures of 350 F. to 450 F. or higher. Numerousthickening agents have been proposed for use in such greases, includingsoap base thickeners, inorganic clay thickeners and organic thickeningagents. Examples of this latter class of thickening agents includevarious polyureas, ureido compounds, aminoaryl diureas, triazines andthe like. Such organic thickening agents are typically prepared byreacting one or more mono-, di-, or polyamines with one or more mono-,di-, or polyisocyanates. Other related organic thickeners includearylcarbamyl compounds formed by reacting an aromatic amine with thereaction product of an aromatic diisocyanate and p-aminobenzoic acid.

While organic thickening agents of the aforementioned types producegreases having desirably high dropping points, this is but one measureof a greases ability to perform satisfactorily at high temperatures.Other important properties include thermal and mechanical stability,high temperatue bearing performance, oxidation and corrosion resistance,etc. While additives are normally incorporated into grease compositionsto improve one or more of these properties, the thickening agent itselfcan significantly affect, either favorably or adversely, the

3,785,979 Patented Jan. 15, 1974 properties of the finished greaseproduct. Thus, in spite of the numerous organic thickening agents knownin the art, there is a continuing need for the development of thickeningagents which will not only produce greases having high dropping points,but which will additionally augment other important propetries of thefinished product. The present invention provides such a class ofthickening agents.

SUMMARY OF THE INVENTION It has now been found that grease compositionshaving excellent high temperature lubricating properties can be producedby incorporating into an. oleaginous base vehicle, a minor amount of adibenzimidazole compound corresponding to the formula:

wherein R and R are aliphatic hydrocarbyl radicals, R is ahydrocarbylene radical, R and R are aromatic hydrocarbylene radicals andX is --O or Not only do the grease compositions of the invention havehigh dropping points, but in addition they have excellent mechanical andthermal stability, and high temperature bearing performance propertiesas well. These excellent qualities are believed attributable in largepart to the unique dibenzimidazole structure of the present thickeningagents which produces an extremely stable molecule.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The aforedescribeddibenzimidazole thickening agents can be conveniently prepared byreacting one mole of a dicarboxylic acid anhydride with two moles of anitrosubstituted phenylenediamine, followed by reduction of the nitrogroups to amine groups, and further reaction with two moles of thereaction product of an aromatic diisocyanate with a monohydric alcoholor monoamine. This procedure is illustrated by the following equations:

Preparation of dibenzimidazole-urea-urethane Equation 2 NH N H 2 C-Ra-CPreparation of dibenzimidazole-urea thickeners Equation 5 Equation 6 Analternative method of preparing the bis-nitrobenzimidazole (intermediateproduct I) employed in Equation 2, is to react the diacrboxylic acid orits anhydride with two moles of a phenylene diamine which is notnitrosubstituted. The resultan product can be subsequently nitrated toproduce bis-nitrobenzimidazole which is then converted to its amino form(intermediate product II) and reacted with two moles of intermediateproducts III or V as shown in Equations 4 and 6, respectively. A moredetailed description of the preparation of the benzimidazole thickenersis given in the examples.

Dicarboxylic acids or anhydrides which can be suitably employed inpreparing the thickeners of the invention include the acids oranhydrides of aliphatic dicarboxylic acids such as succinic, glutaric,adipic, pimelic, suberic, azelaic, sebacic acids or anhydrides, as wellas the anhydrides of aromatic dicarboxylic acids such as phthalic,isophthalic or terephthalic acids or anhydrides or their esters.Cyclohexane dicarboxylic acids and anhydrides such as 1,2- or1,4-cyclohexane dicarboxylic acid or anhydride are likewise suitable asis tetrahydrophthalic acid or anhydride. Hydrocarbyl substituteddicarboxylic acid anhydrides can also be employed, for example, alkyloralkenyl-substituted succinic corresponding to the formula is an alkyl oralkenyl substituent of from 1 to 16 carbon atoms or more. Aliphaticdicarboxylic acid anhydrides are preferred, and in general are selectedso that the R radical of the previously depicted formula has from 2 to20, preferably from 2 to 12 carbon atoms.

Phenylene diamines suitable for preparing the thickening agents of theinvention are ortho-phenylene diamines having a nitro group substitutedthereon, e.g., 4-nitro-ophenylene diamine. In addition to the nitrosubstituent, o-phenylene diamines having other substituents, e.g., alkylor halo substituents, can also be employed provided that suchsubstituents do not appreciably interfere with the reaction of thephenylene diamine with the dicarboxylic acid anhydride.

If the alternative procedure discussed above is employed to prepare thebis-nitrobenzimidazole intermediate, the phenylene diamine need notcontain a nitro substituent since the addition of the nitro groups isaccomplished subsequent to formation of the bis-benzimidazole. Hence,when this procedure is followed, unsubstituted o-phenylene diamine maybe utilized or any other o-phenylene diamine having substituents whichwill not appreciably interfere with the formation of bis-benzimidazoleor its subsequent nitration. Specific examples of such phenylenediamines include 4-chloro-o-phenylene diamine and 3,4- toluene diamine.

Aromatic diisocyanates which may be employed in accordance with theinvention include monoor di-nuclear aromatic diisocyanates having atotal of from 6 to 20 carbon atoms. Such diisocyanates includebiphenylenediisocyanates, naphthylenediisocyanates andmonophenylenediisocyanates including tolylenediisocyanate. Illustrativeof such diisocyanates are 3,3-dimethylbiphenyl-4,4- diisocyanate,diphenylmethane-4,4'-diisocyanate,3,3-dimethyldiphenylmethanet,4-diisocyanate, 2,4-tolylenediisocyanate,1,S-naphthylenediisocyanate and mixtures of 2,4- and2,-tolylenediisocyanates. 2,4-Tolylenediisocyanate and mixtures of 2,4-and 2,6-tolylenediisocyanates are particularly preferred diisocyanatereactants.

Monohydric alcohols which can be suitably employed to prepare thedibenzimidazole-diurethane-diurea thickeners include alphatic alcoholshaving from 8 to 30, preferably from 12 to 24, carbon atoms. Examples ofsuch alcohols include octyl, nonyl, lauryl, tetradecyl, hexadecyl,octadecyl, octadecenyl, eicosyl and docosyl alcohols, etc., and mixturesthereof. Thickeners prepared using stearyl or oleyl alcohols or mixturesthereof have been found to be particularly advantageous.

Monoamines which can be employed to prepare the dibenzimidazole-ureathickeners of the invention are, aliphatic monoamines or those having apredominantly aliphatic character having from 8 to 30, preferably from12 to 24, carbon atoms. Suitable monoamines include octylamine,decylamine, dodecylamine, tetradecylamine hexadecylamine,heptadecylamine, octadecylamine, octadecenylamine, eicosylamine,docosylamine, tetracosylamine, etc. and mixtures thereof.

Mixtures of the above-mentioned monohydric alcohols and monamines canalso be employed thereby producing benzimidazole compounds having bothalkylurethane and alkylurylene terminal groups.

The thickening agents of the invention are generally employed in greasecompositions in an amount sufiicient to gel the oleaginous base vehicleto grease consistency. This amount can vary, for example, from about5-50% 5 by weight of the total composition. Normally, however, thickenerconcentrations of 10-35% by weight are sufficient to impart the desiredconsistency to the inventive compositions.

A wide variety of lubricating oils may be employed as the base vehiclein the present compositions. Suitable base oils include minerallubricating oils such as naphthenic base, paraflin base or mixed baseoils having a viscosity in the range of from 50 SSU at 100 F. to 300 SSUat 210 F.; synthetic hydrocarbon oils such as oligomerized alpha-olefinsand oils derived from coal products; synthetic oils such as alkylenepolymers, alkylene, oxide-type polymers, polyalkene glycols, polyethers,phosphate esters, dicarboxylic acid esters and pentaerythritol esters.The above oils may be used individually or in mixtures thereof, wherevermiscible or made so by the use of solvents. Of the aforementioned baseoils, mineral lubricating oils having viscosities of from about 400 to700 SSU at 100 F. are especially preferred.

In addition to the dibenzimidazole thickeners, the present compositionscan also contain anti-corrosion additives such as disodium sebacate,glyceryl monooleate, sodium sulfonates, sodium nitrite, aminoandhemetriazoles, and isostearamides or imidazolines oftetraethylenepentamine; oxidation inhibitors such asphenyl-alphanaphthylamine, phenyl-beta-naphthylamine, diphenylamines,phenothiazine, dithiocarbamates and various analogs and homologsthereof; viscosity index improvers such as methacrylate polymers andcopolymers; extreme pressure agents, and any other additive recognizedin the art to perform a particular function or functions.

The following examples illustrate the method of preparation of thepresent thickeners and their excellent prop erties. It is to beunderstood, however, that these examples are presented for illustrativepurposes only and that the invention in its broader aspects should notbe limited thereto.

EXAMPLE I Preparation of dibenzimidazole-urea-urethane thickening agentsA 4-liter round bottom flask was charged with 302.2 g. (2 moles) of4-nitro-o-phenylene diamine, 100.0 g. (1 mole) of succinic anhydride and2 liters of 4 normal hydrochloric acid solution. The flask and itscontents were then refluxed, with stirring, for 24 hours. Heating wasdiscontinued and the reactants were cooled to C., filtered, and thefiltrate was discarded. The precipitate was collected and neutralizedwith 1,500 ml. of normal ammonium hydroxide solution, refiltered, andwashed twice with water. The neutralized material resulting wasdissolved in refluxing ethylene glycol, treated with decolorizingcharcoal, filtered and the filtrate cooled. The crystalline precipitatethat appeared was collected, washed with ethanol and dried. The yieldwas 65 grams of 1,2- bis(5-nitrobenzimidazoyl-2)ethane having a meltingpoint of 305 C.

56.04 g. (0.16 mole) of the above product was then suspended in 1,200ml. of 3 normal hydrochloric acid solution to which was added palladiumon charcoal catalyst and reduction of the nitro groups eifected in a lowpressure hydrogenation apparatus. The catalyst was then filtered off,the filtrate neutralized with sodium bicarbonate and the resultingprecipitate collected. After washing with water and drying, 41.5 g. ofl,2-bis(5-aminobenzimidazoyl-2)ethane hydrate was obtained having amelting point of 154155 C.

A 5-liter 3-necked flask equipped with a mechanical stirrer was chargedwith 2 liters of chloroform and 522 g. (3 mole) of commercial grade2,4-tolylenediisocyanate. To this stirred solution was added 270 g. (1mole) of stearyl alcohol over a period of 2 hours. After the addition,the contents of the flask were poured into 3 liters of hexane and cooledovernight. The resulting precipitate, N-(3isocyanato-4-methylphenyl)octadecyl carbamate,

was collected and reprecipitated from hexane and vacuum dried. Theproduct had a melting point of 78-79 C.

17.54 g. (0.06 mole) of the previously formed 1,2-bis-(S-amino-benzimidazoyl-Z)ethane was placed into a 500 ml. resin flaskequipped with a mechanical stirrer together with 53.4 g. (0.12 mole) ofN-(3-isocyanato-4- methylphenyl)octadecyl carbamate .in 573 g. of a HVIneutral oil having a viscosity of 70 at 210 F. This suspension washeated with stirring, under nitrogen, to 127 C. When the reaction wascomplete, the contents were cooled to approximately C. The formulationwas then milled three times in a three-roll paint mill. The resultinggrease (Grease 1) contained 11.0% by weight thickener and had an ASTMunworked penetration (P of 212 and a worked penetration (P of 264.

EXAMPLE II Preparation of dibenzimidazole-urea thickening agents Theprocedure of Example I was essentially repeated except that 269 g. (1mole) of stearylamine was reacted with 2,4-tolylenediisocyanate in placeof stearyl alcohol thereby forming N-(3-isocyanato-4-methylphenyl)octadecyl carbamide.

35.5 g. (0.08 moles) of the carbamaide intermediate was then reactedwith 11.7 g. (0.04 mole) of 1,2-bis(5- aminobenzimidazoyl-Z)ethaneprepared as in Example I in 382 g. of a HVI neutral oil having aviscosity of 70 at 210 F. After completion of the reaction, the contentswere cooled and milled three times in a three-roll paint mill. Theresulting grease (Grease 2) contained 11.0% by Weight thickener and hadan ASTM unworked penetration (P of 268 and a worked penetration (P of283.

EXAMPLE III The procedure of Example I was essentially repeated exceptthat a 60.40 molar ratio of stearyl and oleyl alcohols were employed inplace of the stearyl alcohol reactant in Example I. The resulting greasecontained 9.5% by weight thickener and had an ASTM unworked penetration(P of 197 and a worked penetration (P of 253.

EXAMPLE IV EXAMPLE V In order to demonstrate the excellent hightemperature performance characteristics of the present greasecompositions, the greases of Example I and III were subjected to twodifferent high temperature bearing tests. The results of these tests areshown in the following table.

TABLE I Test procedure Grease 1 1 Grease 3 1 Navy high speed bearingtest (Fed. test Mtd. No. 331.1) 300 F., 10,000 r.p.m.bearing hie. hours4, 322, 5,118 4,956+ ABEC hearing test (Fed. test Mtd. No. 333) 350 F.,10,000 r.p.m.hours to failure I 386 2 465 Includes 1% wt.phenyl-alpha-naphthylamine, 0.5% Oronite 250 dilaulryl selenide), 1% wt.sodium sebaeate and 0.03% wt. 3-amino-1,2,4-

I'IBZO e.

2 Average of two runs.

3 ,7 8 5,979 7 8 EXAMPLE VI 2. The composition of claim 1 wherein thedibenzimid- Other dibenzimidazole thickeners and greases in accord-31016 compound is Present in the amount of from 5 to 50% ance with theinvention include those shown in the followby weight.

ing table.

TABLE II Grease compo- Base sition Acid or anhydride Phenylene diann'neDiisocyanate Alcohol r amine oil Suceinic anhydride 4-nitro-o-phenylenediarnine... 2,4-toiylene-diisocyanate 80% mole 01231137011; mole OIBHM NH1- A 6 Adipio acid" do 3,3-dimethyl-diphenyl- 100% mole C1sH37NH3 Am%thane-4,4'-diisoeya- 118. B 7...-.-..... l,2-cyclglhieixanedicarboxyiic do 2,4-to1ylene-diisoeyanate... 70% mole CzoHnNHz; 30% moleCnHzs B a y 9. a. 8 Dodecyl succinic anhydride d03,3-dimethyl-biphenyl-4, 100% mole C H OH B 4-diisocyanate. 9 Phthalieanhydrifl do 2,4tolylene-diis0oyanate.. 7578 1:[nole CIBHMOH; mole0161133 0 Norm-Base oil A=Mineral lubricating oil having a viscosity of500 SSU at 100 F. Base oil B=Minera1inbzicating oil having a viscosityat 70 SSU at 210 F. Base oil C=Mixture of hexadecyl isostearate anddimer acid esters.

I claim as my invention: 3. The composition of claim 1 wherein X is-O-. 1. A grease composition consisting essentially of a 4. Thecomposition of claim 1 wherein X is major amount of a lubricated oil andin an amount suf- H ficient to thicken the lubricating oil to greaseconsistency,

25 -N- a dibenzimidazole compound corresponding to the forl 5. Thecomposition of claim 1 wherein R is an alkylene radical having from 2 to12 carbon atoms.

6. The composition of claim 1 wherein the R and R E H H E H have from 12to 24 carbon atoms. 7. The composition of claim 6 wherein R and R aretolylene. 8. The composition of claim 7 wherein R is ethylene. g 9. Thecomposition of claim 8 where R and R have N o O 16 to 18 carbon atoms.

H H H l 10. The composition of claim 9 wherein the lubricating R oil isa mineral lubricating oil.

N References Cited H UNITED STATES PATENTS 3,015,625 1/1962 Rosscup etal. 25251.5 A 3,133,883 5/1964 Hayne et a1. 252-515 A wherein R and Rare aliphatic hydrocarbyl radicals hav- 3,222,235 12/19 5 Rai et al.25250 X ing 6 to 30 carbon atoms, R is a hydrocarbylene radical havingfrom 2 to 20 carbon atoms, R and R are aro- PATRICK GARVIN, 'Y EXamlnermatic hydrocarbylene radicals having from 6 to 20 car- A METZ, AssistantExaminer bon atoms and X is -O- or U.S. Cl. X.R.

